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Control apparatus of semiconductor switch

a control apparatus and semiconductor technology, applied in relays, emergency protective arrangements for limiting excess voltage/current, pulse techniques, etc., can solve the problems of increasing the temperature of the channel of this mosfet ta, increasing the power loss of the mosfet ta, and shortening the judging time. , to achieve the effect of shortening the judging time, increasing the discrimination precision, and quickly cutting off the circui

Inactive Publication Date: 2010-09-07
YAZAKI CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention provides a control apparatus for a semiconductor switch that can quickly detect and turn off a shortcircuit current, minimizing power loss and temperature increase. The control apparatus includes a semiconductor switch, a counter electromotive force judging unit, and a control unit. The counter electromotive force judging unit determines whether a counter electromotive force produced on a first wiring line exceeds a threshold value. The control unit then controls the semiconductor switch to turn off, as long as the counter electromotive force exceeds the threshold value. The control apparatus can quickly discriminate between a shortcircuit current and a rush current, allowing for the use of semiconductor elements with smaller capacities and reducing production costs. The increased gradient of the shortcircuit current is used as a judging value, ensuring accurate detection of the shortcircuit current. The control apparatus can also reduce power loss by quickly detecting and turning off the shortcircuit current.

Problems solved by technology

If a large current flows under this condition, then a power loss of the MOSFET TA is increased.
In the case of FIG. 10, since the current ID is increased after the present time has passed through the point B2, the power loss of the MOSFET TA becomes large value, which may cause a temperature of the channel of this MOSFET TA to be increased.
In other words, such an element having a small chip size cannot be used, so that a design freedom is restricted, which may cause a cost-up factor.
Also, there is another problem in fluctuations of the reference current Iref.
Any of these solving methods may cause the cost-up factor.
Similarly, this solving method may cause the cost-up factor.
As a result, when the peak value of the rush current is increased, the time required to be reached to the judging value is prolonged, so that the judgement as to the occurrence of the shortcircuit is delayed, and therefore, the timing when the shortcircuit current is cut off is delayed.
As a consequence, the power loss of the semiconductor element is increased, so that such a problem may occur.

Method used

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  • Control apparatus of semiconductor switch
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  • Control apparatus of semiconductor switch

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second embodiment

[0087]Furthermore, if the shortcircuit judging value is set to be direct proportion to the power supply voltage VB, then this shortcircuit judging value can be set to be a smaller judging value. This value setting condition will be explained in a second embodiment later.

[0088]Next, a description is made of a method for detecting the counter electromotive force E1 short in the circuit shown in FIG. 1. Since such a circuit, in which the resistors R1 and R2 are series-connected to the capacitor C1, is arranged between the point P1 and the ground as the counter electromotive circuit 13, while the load 11 is operated under the normal condition, a voltage V3 at the non-grounded terminal of the capacitor C1 is charged up to the voltage V1 of the point P1. Since a voltage drop caused by that the load current ID flows through the first wiring line is small under the normal condition, the non-grounded terminal voltage V3 is nearly equal to the power supply voltage VB.

first embodiment

[0089]This voltage V3 at the non-grounded terminal of the capacitor C1 may constitute a reference voltage when the magnitude of the counter electromotive force E1 is measured. In accordance with this first embodiment, when the counter electromotive force E1 is generated and thus the voltage V1 at the point P1 is lowered, it is so judged as to whether or not a shortcircuit current flows by measuring a difference voltage between this voltage V1 and the reference voltage V3.

[0090]In other words, in such a case that the difference voltage (V3−V1) exceeds a preset threshold voltage, such a judgment is made that the short current flows in the circuit. Then, this difference voltage (V3−V1) constitutes a voltage appeared at both the terminals of the resistors R1 and R2. In this first embodiment, such a voltage across both the terminals of the resistor R1 is measured as a voltage which is partially produced in the first-mentioned voltage, so that an occurrence of such a shortcircuit current ...

third embodiment

[0130]In this third embodiment, in the case that a shortcircuit / grounding event happens to occur in any one of these plural FET channels, all of these channels are once turned OFF, and thereafter, the respective channels are sequentially and again turned ON in a constant interval so as to specify such an FET channel that the shortcircuit / grounding event occurs. This detecting operation may be carried out by a logic circuit.

[0131]FIG. 7 is a circuit diagram for indicating a sequential starting circuit for 5 channels as one example of the above-explained logic circuit. As indicated in this drawing, the sequential starting circuit includes switches SW1 to SW5, AND circuits AND11 to AND19, D type flip-flops DF11 to DF15, exclusive-NOR circuits XNOR1 to XNOR5, and also, a dock circuit CL. The switches SW1 to SW5 turn ON / OFF the MOSFETs owned by each of load circuits for 5 channels. Then, output signals SW11 to SW15 of the AND circuits AND11 to AND15 are supplied to the input terminal of ...

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Abstract

A control apparatus includes a semiconductor switch that is arranged between a DC power supply and a load to control a turning ON / OFF operation of the load, a counter electromotive force judging unit that determines whether a counter electromotive force produced on a first wiring line is greater than a threshold voltage, the first wiring line connecting the semiconductor switch to the DC power supply, and a control unit that controls the semiconductor switch so as to be turned OFF when the counter electromotive force judging unit determines that the counter electromotive force is greater than the threshold voltage.

Description

BACKGROUND OF THE INVENTION[0001]The present invention is related to a control apparatus of a semiconductor switch provided between a DC power supply and a load, for turning ON / OFF the load. More specifically, the present invention is directed to a technique capable of protecting the semiconductor switch when a shortcircuit current is produced.[0002]Loads (electric appliances) such as, for instance, a motor for driving a power window, or a lamp, which are mounted on a vehicle are driven by applying a DC voltage from a battery functioning as a DC power supply to the loads. In this case, since a semiconductor switch such as a MOSFET and the like, which is provided between a load and the battery, is turned ON / OFF so that this load is controlled so as to be driven / stopped.[0003]Also, in a case that an overcurrent protecting apparatus is mounted, an overcurrent protecting apparatus immediately turns OFF the semiconductor switch for protecting both a circuit and a load when the overcurren...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): H02H3/08H01H47/00H03K17/04H03K17/082
CPCH03K17/0822H02H3/08H02H7/20
Inventor OHSHIMA, SHUNZOU
Owner YAZAKI CORP
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